does not work the rule, to exclude the folder in the .gitignore file, which lies in the project folder.

Rule:

git still does not ignore the .idea folder:

What am I doing wrong?

Answer 1, Authority 100%

You do everything right and this will exclude the .idea folder from the potential addition of Untracked files. Your problem is that .idea already in the repository. I must first exclude it from there, and then it will not try to penetrate there.
Try to do:

git rm -r --cached .idea